Synthesis of 3-fluoro-3-methyl-3-silatetrahydropyran and its conformational preferences in gas and solution by GED, NMR and theoretical calculations. Issue 15 (12th April 2018)

• Record Type: Journal Article
• Authors: Kirpichenko, Svetlana V.; Shainyan, Bagrat A.; Kleinpeter, Erich; Shlykov, Sergey A.; Phien, Tran Dinh; Albanov, Alexander I.
• Is Part Of: Tetrahedron. Volume 74:Issue 15(2018)
• Page Start: 1859
• Page End: 1867
• Publication Date: 2018-04-12
• Subjects: 3-Fluoro-3-methyl-3-silatetrahydropyran -- Conformational analysis -- Gas phase electron diffraction -- Low-temperature NMR -- DFT -- MP2 and CCSD(T) calculations; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2018.02.055
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: The 3, 3-disubstitued 3-silaheterocyclohexane with an electronegative substituent at silicon, 3-fluoro-3-methyl-3-silatetrahydropyran1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED) and low temperature 13 C and 19 F NMR spectroscopy. Quantum-chemical calculations were carried out both for the isolated species and H-complexes in gas and in polar medium. The predominance of the1 -Feq Meax conformer (1 -Feq :1 -Fax ratio of 65:35, ΔG° = 0.37 kcal/mol) determined from GED is close to the theoretically estimated conformational equilibrium, especially at the DFT level. In solution, low temperature NMR spectroscopy showed no decoalescence of the signals in 13 C (down to 95 K) and 19 F NMR spectra (down to 123 K). However, the calculated 19 F chemical shift of −173.6 ppm for the1 -Feq Meax conformer practically coincides with the experimentally observed value (−173 to −175 ppm) as distinct from that for the1 -Fax Meeq conformer (−188.8 ppm), suggesting compound1 to be anancomeric in solution, in compliance with its theoretical and experimental preference in the gas phase. Graphical abstract: